Anyone Know why the MC 4 canopy has a large grommet

[kenneth21441 0]

I have often wondered why the MC 4 canopy has a large grommet placed on the center cell near the bridle line attachment. I've looked it all over the T.O. and found no information or use for it like attaching a static line or center line to it or so forth.
The only thing that I could come up with was as a way to release some of the internal pressures during opening like that of the vent cap on the MC1 and T10 series rounds.
Ive tried to email Para-flight on this question to no aval.

Does any one have any ideals on this.?


Thanks,

Kenneth Potter
FAA Senior Parachute Rigger
Tactical Delivery Instructor (Jeddah, KSA)
FFL Gunsmith

[dragon2 2]

Only canopies I know of that had a hole there had it for a reefing line.

ciel bleu,
Saskia

[kenneth21441 0]

But thats basically what the slider is suppose to do. In reference to the reefing lines that are used on the Large cargo parachutes to slow the opening down.

Maybe this was added in the design factor to add a reefing or maybe a center line.

Kenneth Potter
FAA Senior Parachute Rigger
Tactical Delivery Instructor (Jeddah, KSA)
FFL Gunsmith

[dragon2 2]

I was thinking more along the lines of "how old is the design for that canopy". One older precision jumping canopies I sold had a reefing line, easy enough to convert the canopy to a normal slider if you want (and you want LOL).
Maybe the grommet is a leftover from that and they didn't change the design all the way?

Just guessing here

ciel bleu,
Saskia

[kenneth21441 0]

Before the MC4 design there was the MT1xx model from I believe to be in the early to mid 80's knowing how are government works this design could be from the 70's. Who knows.

But I remember the MC4 series coming out in the early part of the 90's as a replacement for the Mt1.

Just cant figure out why the Mt1 does not have this gromment and the MC4 does?

Kenneth Potter
FAA Senior Parachute Rigger
Tactical Delivery Instructor (Jeddah, KSA)
FFL Gunsmith

[Davemon 0]

The MC-4 drawings do not show a grommet on the canopy near the bridle attachment. The MC-5 canopy does use a drogue controlled slider for the double bag static line deployment so perhaps that is the canopy you have. Check the part number on the stamp and that should be a clue.

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Before the MC4 design there was the MT1xx model from I believe to be in the early to mid 80's knowing how are government works this design could be from the 70's. Who knows.

But I remember the MC4 series coming out in the early part of the 90's as a replacement for the Mt1.

Just cant figure out why the Mt1 does not have this gromment and the MC4 does?

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[ripcord4 0]

My copy of TM 10-1672-287-23&P for the MC4 DOES indeed show the grommet just aft of the main pilot chute bridle attaching ring. However, there is nothing in the text to indicate what it is for.

[darkwing 5]

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...The only thing that I could come up with was as a way to release some of the internal pressures during opening like that of the vent cap on the MC1 and T10 series rounds.
...

I don't think that can be the case. There would be better ways of doing it, and I don't think it would be very effective at that anyway. I am curious what a single grommet in the top skin would be for. None of the possibilities I can think of make any sense. So I'll wait for someone smarter to chime in.

-- Jeff
My Skydiving History

[jumper03 0]

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...The only thing that I could come up with was as a way to release some of the internal pressures during opening like that of the vent cap on the MC1 and T10 series rounds.
...

I don't think that can be the case. There would be better ways of doing it, and I don't think it would be very effective at that anyway. I am curious what a single grommet in the top skin would be for. None of the possibilities I can think of make any sense. So I'll wait for someone smarter to chime in.

I work with an old Halo rigger (old man Greg most of you might know) and a master rigger from the Test board (ratboy). So I posed the question to them.

They both said it has something to do with the lighting system that is on the top skin of the mc-4 that wasn't on the mt-1x.

I would relay more questions but there is no way in hell I can type all that greg has to say about anything...

Scars remind us that the past is real

[riggerrob 643]

If it is a large (number 8) grommet, it is probably for a pilot chute controlled reefing system.
PCR usually has a bridle twice as long as the suspension lines. One end of the bridle is tied to the base of the pilot chute, while the other end is routed through the large grommet, through a pulley (or ring) on (top dead center) slider and then tied to the center cell. This doubles the reefing force of the pilot chute and doubles the time to inflate.
PCR is only relevant when deploying a canopy at airspeeds significantly faster than "skydiver terminal" (120 miles per hour), so is only seen on military HAHO canopies and a few competition accuracy canopies.

PCR is a vast simplification of the old ropes-and-rings reefing system.

[LouDiamond 1]

You are in luck, I was speaking to the people at Para-flite and I remembered this question. The grommet was initially installed on the cotton buffer of MC-4 series canopies when a static line requirement was identified, but it never came to fruition. The MC-5 subsequently came out and the installation of grommets on MC-4 canopies was discontinued. The mentioned lighting system was a different project and has no relation to the grommet I was told. As has been mentioned, the grommet served to allow for the installation of a reefing system similar to that seen on the MC-5 and other mfgrs systems to date.

"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

[kenneth21441 0]

I would like to thank everyone for the input on this subject as it was just a mind blower going through the manual and not seeing anything on the subject. But then you look at the canopy and there it is a gromment that has not a single use, except to let more air pass through it.... verses having some material over it.

Ive got three of these canopies and now know what to do with them more so. Jumpem all and let the nylon hit the air.

Thanks once again and love how this information is able to be passed down so fast.

thanks,

Kenneth Potter
FAA Senior Parachute Rigger
Tactical Delivery Instructor (Jeddah, KSA)
FFL Gunsmith

[jumper03 0]

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The mentioned lighting system was a different project and has no relation to the grommet I was told.

SWEET!!! I can school greg on something this weekend!!

Scars remind us that the past is real

[dragon2 2]

That's what the reefing line was for? I thought it was an older design before the slider was perfected, or something. Why would you jump an accuracy canopy with >120 mph speed? Style?

I had no clue how to pack all that bridle I just sent the rig fieldpacked to the buyer Last guy to jump it during a competition here didn't know how to pack it either Presto, reserve!

ciel bleu,
Saskia

[riggerrob 643]

Sail sliders work great up about 150 mph, but deploying faster than that requires a more complex reefing system.
Style competitors try to fall as fast as possible (much faster than 120 mph) - when turning freefall maneuvers - so need a better reefing system. The other factor for style and accuracy competitors is the huge nose openings on Para-Foils and Eiff Challenger Classic canopies. Those huge inlets are great for keeping the canopy inflated at steep angles of attack - near the stall - but tend to scoop air too quickly during opening, resulting in hard openings. Ergo, accuracy canopies open great during hop-and-pops, but open too hard at "competition terminal" velocity.
Military HAHO jumpers are always at the heavy-weight, high-speed end of the scale, routinely exceeding 150 mph, ergo, they also need better reefing systems than sail sliders.

[dragon2 2]

Makes sense, thanx.

ciel bleu,
Saskia